1. Field of the Invention
The present invention relates to a lens module, and more particularly, to a lens module capable of easily performing position correction for an optical axis alignment because a decentered lens may be easily recognized without any shape deformation of laminated lenses.
2. Description of the Related Art
In a general lens module used in a mobile phone etc., lenses manufactured through an injection molding or processing are sequentially laminated in a barrel having a predetermined-sized internal space. A spacer is disposed between the lenses in order to maintain a predetermined distance between the lenses. The laminated lenses and the spacer are fixed using a press-fit ring.
Especially, an external diameter of the lens is manufactured so as to be smaller or greater than an inside diameter of the barrel because a processing error and a formation error may occur during manufacture of the lens and the barrel.
In this case, a size of a decenter from an optical axis is determined according to the tolerance relation between the lens and the barrel.
When the inside diameter of the barrel is greater than the external diameter of the lens, stress on the lens decreases while the size of the decenter between lenses increases.
On the contrary, when the inside diameter of the barrel is smaller than the external diameter of the lens, the lenses must be forcedly fitted into the barrel.
In this forcedly-fitting manner, there is a limitation in that the lens and the barrel are weak to a thermal deformation and a plastic deformation because the lens and the barrel are generally formed of a thermoplastic resin. Accordingly, the lenses may be deformed by heat and friction during the forcedly-fitting process although the size of the decenter decreases.
When a plurality of lenses are laminated, it is not easy to find which lens is decentered. This causes an optical axis correction to be substantially difficult, resulting in the defectiveness of the product.
Despite a recent tendency to require a high precision lens in order to face a high resolution pixel technology, a related art method of manufacturing a lens module has a limitation in that it is substantially impossible to manufacture a precision lens module.